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Simplify impl_Display macro
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Guillaume Gomez
parent
125db409ff
commit
884e0f0a68
@ -208,7 +208,7 @@ static DEC_DIGITS_LUT: &[u8; 200] = b"0001020304050607080910111213141516171819\
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8081828384858687888990919293949596979899";
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macro_rules! impl_Display {
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($($t:ident => $size:literal $(as $positive:ident in $other:ident)? => named $name:ident,)* ; as $u:ident via $conv_fn:ident named $gen_name:ident) => {
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($($t:ident => $size:literal $(as $positive:ident)? named $name:ident,)* ; as $u:ident via $conv_fn:ident named $gen_name:ident) => {
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$(
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#[stable(feature = "rust1", since = "1.0.0")]
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@ -222,102 +222,105 @@ macro_rules! impl_Display {
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{
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if !is_nonnegative {
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// convert the negative num to positive by summing 1 to its 2s complement
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return $other((!self as $positive).wrapping_add(1), false, f);
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return (!self as $positive).wrapping_add(1)._fmt(false, f);
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}
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}
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#[cfg(feature = "optimize_for_size")]
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{
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if !is_nonnegative {
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// convert the negative num to positive by summing 1 to its 2s complement
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return $other((!self.$conv_fn()).wrapping_add(1), false, f);
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return $gen_name((!self.$conv_fn()).wrapping_add(1), false, f);
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}
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}
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)?
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// If it's a positive integer.
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#[cfg(not(feature = "optimize_for_size"))]
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{
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$name(*self, true, f)
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self._fmt(true, f)
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}
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#[cfg(feature = "optimize_for_size")]
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{
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$gen_name(*self, true, f)
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$gen_name(self.$conv_fn(), true, f)
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}
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}
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}
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#[cfg(not(feature = "optimize_for_size"))]
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fn $name(mut n: $t, is_nonnegative: bool, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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let mut buf = [MaybeUninit::<u8>::uninit(); $size];
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let mut curr = buf.len();
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let buf_ptr = MaybeUninit::slice_as_mut_ptr(&mut buf);
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let lut_ptr = DEC_DIGITS_LUT.as_ptr();
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impl $t {
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fn _fmt(mut self: $t, is_nonnegative: bool, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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let mut buf = [MaybeUninit::<u8>::uninit(); $size];
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let mut curr = $size;
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let buf_ptr = MaybeUninit::slice_as_mut_ptr(&mut buf);
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let lut_ptr = DEC_DIGITS_LUT.as_ptr();
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// SAFETY: Since `d1` and `d2` are always less than or equal to `198`, we
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// can copy from `lut_ptr[d1..d1 + 1]` and `lut_ptr[d2..d2 + 1]`. To show
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// that it's OK to copy into `buf_ptr`, notice that at the beginning
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// `curr == buf.len() == 39 > log(n)` since `n < 2^128 < 10^39`, and at
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// each step this is kept the same as `n` is divided. Since `n` is always
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// non-negative, this means that `curr > 0` so `buf_ptr[curr..curr + 1]`
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// is safe to access.
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unsafe {
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// need at least 16 bits for the 4-characters-at-a-time to work.
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#[allow(overflowing_literals)]
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#[allow(unused_comparisons)]
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// This block will be removed for smaller types at compile time and in the worst
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// case, it will prevent to have the `10000` literal to overflow for `i8` and `u8`.
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if core::mem::size_of::<$t>() >= 2 {
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// eagerly decode 4 characters at a time
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while n >= 10000 {
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let rem = (n % 10000) as usize;
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n /= 10000;
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// SAFETY: Since `d1` and `d2` are always less than or equal to `198`, we
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// can copy from `lut_ptr[d1..d1 + 1]` and `lut_ptr[d2..d2 + 1]`. To show
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// that it's OK to copy into `buf_ptr`, notice that at the beginning
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// `curr == buf.len() == 39 > log(n)` since `n < 2^128 < 10^39`, and at
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// each step this is kept the same as `n` is divided. Since `n` is always
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// non-negative, this means that `curr > 0` so `buf_ptr[curr..curr + 1]`
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// is safe to access.
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unsafe {
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// need at least 16 bits for the 4-characters-at-a-time to work.
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#[allow(overflowing_literals)]
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#[allow(unused_comparisons)]
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// This block will be removed for smaller types at compile time and in the worst
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// case, it will prevent to have the `10000` literal to overflow for `i8` and `u8`.
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if core::mem::size_of::<$t>() >= 2 {
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// eagerly decode 4 characters at a time
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while self >= 10000 {
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let rem = (self % 10000) as usize;
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self /= 10000;
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let d1 = (rem / 100) << 1;
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let d2 = (rem % 100) << 1;
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curr -= 4;
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let d1 = (rem / 100) << 1;
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let d2 = (rem % 100) << 1;
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curr -= 4;
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// We are allowed to copy to `buf_ptr[curr..curr + 3]` here since
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// otherwise `curr < 0`. But then `n` was originally at least `10000^10`
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// which is `10^40 > 2^128 > n`.
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ptr::copy_nonoverlapping(lut_ptr.add(d1 as usize), buf_ptr.add(curr), 2);
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ptr::copy_nonoverlapping(lut_ptr.add(d2 as usize), buf_ptr.add(curr + 2), 2);
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// We are allowed to copy to `buf_ptr[curr..curr + 3]` here since
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// otherwise `curr < 0`. But then `n` was originally at least `10000^10`
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// which is `10^40 > 2^128 > n`.
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ptr::copy_nonoverlapping(lut_ptr.add(d1 as usize), buf_ptr.add(curr), 2);
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ptr::copy_nonoverlapping(lut_ptr.add(d2 as usize), buf_ptr.add(curr + 2), 2);
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}
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}
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// if we reach here numbers are <= 9999, so at most 4 chars long
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let mut n = self as usize; // possibly reduce 64bit math
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// decode 2 more chars, if > 2 chars
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if n >= 100 {
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let d1 = (n % 100) << 1;
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n /= 100;
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curr -= 2;
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ptr::copy_nonoverlapping(lut_ptr.add(d1), buf_ptr.add(curr), 2);
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}
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// if we reach here numbers are <= 100, so at most 2 chars long
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// The biggest it can be is 99, and 99 << 1 == 198, so a `u8` is enough.
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// decode last 1 or 2 chars
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if n < 10 {
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curr -= 1;
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*buf_ptr.add(curr) = (n as u8) + b'0';
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} else {
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let d1 = n << 1;
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curr -= 2;
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ptr::copy_nonoverlapping(lut_ptr.add(d1), buf_ptr.add(curr), 2);
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}
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}
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// if we reach here numbers are <= 9999, so at most 4 chars long
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let mut n = n as usize; // possibly reduce 64bit math
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// decode 2 more chars, if > 2 chars
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if n >= 100 {
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let d1 = (n % 100) << 1;
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n /= 100;
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curr -= 2;
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ptr::copy_nonoverlapping(lut_ptr.add(d1), buf_ptr.add(curr), 2);
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}
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// if we reach here numbers are <= 100, so at most 2 chars long
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// The biggest it can be is 99, and 99 << 1 == 198, so a `u8` is enough.
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// decode last 1 or 2 chars
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if n < 10 {
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curr -= 1;
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*buf_ptr.add(curr) = (n as u8) + b'0';
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} else {
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let d1 = n << 1;
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curr -= 2;
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ptr::copy_nonoverlapping(lut_ptr.add(d1), buf_ptr.add(curr), 2);
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}
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// SAFETY: `curr` > 0 (since we made `buf` large enough), and all the chars are valid
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// UTF-8 since `DEC_DIGITS_LUT` is
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let buf_slice = unsafe {
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str::from_utf8_unchecked(
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slice::from_raw_parts(buf_ptr.add(curr), buf.len() - curr))
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};
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f.pad_integral(is_nonnegative, "", buf_slice)
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}
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// SAFETY: `curr` > 0 (since we made `buf` large enough), and all the chars are valid
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// UTF-8 since `DEC_DIGITS_LUT` is
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let buf_slice = unsafe {
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str::from_utf8_unchecked(
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slice::from_raw_parts(buf_ptr.add(curr), buf.len() - curr))
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};
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f.pad_integral(is_nonnegative, "", buf_slice)
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})*
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#[cfg(feature = "optimize_for_size")]
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fn $gen_name(mut n: $u, is_nonnegative: bool, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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// 2^128 is about 3*10^38, so 39 gives an extra byte of space
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let mut buf = [MaybeUninit::<u8>::uninit(); 39];
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let mut curr = buf.len();
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let buf_ptr = MaybeUninit::slice_as_mut_ptr(&mut buf);
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@ -523,16 +526,16 @@ macro_rules! impl_Exp {
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mod imp {
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use super::*;
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impl_Display!(
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i8 => 3 as u8 in fmt_u8 => named fmt_i8,
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u8 => 3 => named fmt_u8,
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i16 => 5 as u16 in fmt_u16 => named fmt_i16,
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u16 => 5 => named fmt_u16,
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i32 => 10 as u32 in fmt_u32 => named fmt_i32,
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u32 => 10 => named fmt_u32,
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i64 => 19 as u64 in fmt_u64 => named fmt_i64,
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u64 => 20 => named fmt_u64,
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isize => 19 as usize in fmt_usize => named fmt_isize,
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usize => 20 => named fmt_usize,
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i8 => 3 as u8 named fmt_i8,
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u8 => 3 named fmt_u8,
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i16 => 5 as u16 named fmt_i16,
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u16 => 5 named fmt_u16,
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i32 => 10 as u32 named fmt_i32,
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u32 => 10 named fmt_u32,
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i64 => 19 as u64 named fmt_i64,
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u64 => 20 named fmt_u64,
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isize => 19 as usize named fmt_isize,
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usize => 20 named fmt_usize,
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; as u64 via to_u64 named fmt_u64
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);
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impl_Exp!(
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@ -545,18 +548,18 @@ mod imp {
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mod imp {
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use super::*;
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impl_Display!(
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i8 => 3 as u8 in fmt_u8 => named fmt_i8,
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u8 => 3 => named fmt_u8,
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i16 => 5 as u16 in fmt_u16 => named fmt_i16,
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u16 => 5 => named fmt_u16,
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i32 => 10 as u32 in fmt_u32 => named fmt_i32,
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u32 => 10 => named fmt_u32,
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isize => 10 as usize in fmt_usize => named fmt_isize,
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usize => 10 => named fmt_usize,
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i8 => 3 as u8 named fmt_i8,
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u8 => 3 named fmt_u8,
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i16 => 5 as u16 named fmt_i16,
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u16 => 5 named fmt_u16,
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i32 => 10 as u32 named fmt_i32,
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u32 => 10 named fmt_u32,
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isize => 19 as usize named fmt_isize,
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usize => 20 named fmt_usize,
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; as u32 via to_u32 named fmt_u32);
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impl_Display!(
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i64 => 19 as u64 in fmt_u64 => named fmt_i64,
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u64 => 20 => named fmt_u64,
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i64 => 19 as u64 named fmt_i64,
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u64 => 20 named fmt_u64,
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; as u64 via to_u64 named fmt_u64);
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impl_Exp!(i8, u8, i16, u16, i32, u32, isize, usize as u32 via to_u32 named exp_u32);
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